In recent years, a treatment instrument for an endoscope has been known in which a pair of forceps or the like for gripping a tissue are provided at the distal end of a treatment area (for example, refer to Patent Document 1). When a treatment is performed on a tissue in a body cavity using such forceps or the like, it is necessary to adjust the opening and closing direction of the forceps since the opening and closing direction of the forceps projected into the body cavity is not suitable for the position of a tissue to be treated.
In the treatment instrument for an endoscope described in Patent Document 1, an operation shaft member for opening and closing a pair of forceps is connected to a slider. Additionally, the forceps are fixed to an insertion tube through which an operation shaft member is inserted so as not to be rotatable around the axis, and the proximal end of the insertion tube is fixed to an operation portion.
Accordingly, in a case where the opening and closing direction of the forceps is adjusted, a user rotates the overall operation portion around the axis. Then, the insertion tube rotates around the axis, and finally the forceps rotate around the axis, thereby adjusting the opening and closing direction.